Programmable sewing machines are known in the art of textile manufacturing to perform certain repetitive stitching functions in the manufacturing process. Programmable sewing machines are useful for repetitive stitching operations since numerous sewing patterns may be stored in a computer memory and subsequently accessed by an operator. Such sewing patterns can be used to produce a desired stitching design on the given material, namely by moving the material relative to the sewing needle with a clamp assembly (i.e., an arch clamp and a lower clamp plate which may be moved in both in the "X" and "Y" directions) which appropriately engages and moves the material relative to a sewing needle.
Programmable sewing machines, namely the clamp assembly, typically have a maximum range of motion in the "X" direction which is defined by the spacing between two limit switches on the machine. For example, when the limit switch spacing is two inches, the maximum range of motion of the clamp assembly is two inches. However, models are available with various ranges of motion such as a 2-inch, 4-inch, and 6-inch range. Regardless of the spacing, the limit switches are tripped in one commercially available machine by a one-piece tripping plate which is interconnected with the clamp assembly. When the clamp assembly is moving in one direction and the tripping plate trips a limit switch, the clamp assembly will be prevented from further movement in that direction. Similarly, the other limit switch limits movement of the clamp assembly in the opposite direction when tripped by the one-piece tripping plate.
In some instances, it may be desirable for the operator of a programmable sewing machine to obtain a range of motion of the clamp assembly which is slightly more than the maximum range of motion, without purchasing an upgraded and more expensive model with increased range capacity. Prior to the present invention, in one commercially available machine it was not possible to modify the machine to obtain a range of motion of the clamp assembly greater than the maximum range of motion of the machine without extensive modifications to the internal structure of the machine and which typically involved replacing pertinent components with "larger" components (e.g., widening the spacing of the limit switches and replacing the one-piece tripping plate with a larger one-piece tripping plate). Moreover, in some cases the expansion of the range of motion was only in one direction.
Accordingly, it is an object of the present invention to provide a means for extending the range of motion of the clamp assembly which does not require significant modification of the machine. It is a related object of the present invention to provide a two-piece tripping plate assembly that replaces an existing one-piece tripping plate of a programmable sewing machine to expand the range of motion of its clamp assembly, preferably in both directions.